In today's wireless communication networks, user devices such as electronic book readers, cellular telephones, personal digital assistants (PDAs), portable media players, tablet computers and netbooks typically have to search for cells rather frequently. A cell belongs to a public land mobile network (PLMN) that provides land mobile telecommunications service to user devices. Generally, each service provider operates its own PLMN.
When a user device is first powered on, the user device typically first looks for a cell on which the user device was previously camped on, and if that cell is not found, the user device searches for other cells in the frequency band of the cell on which the user device previously was camped. If such a search does not result in finding a cell, a user device typically starts a cell search procedure that involves scanning all carrier frequencies in the available frequency bands. In addition, a user device performs a cell search after losing service or coverage or as part of a periodic scan for a higher priority PLMN.
Cell selection techniques in Global Systems for Mobile Communications (GSM), Wideband Code-Division Multiple Access (WCDMA) systems and other wireless technologies typically assume a fixed channel bandwidth while searching for suitable cells to camp on. For example, in WCDMA systems, channel bandwidth is always 5 MHz. Hence, when a user device performs a WCDMA cell search, the user device can always use channel bandwidth of 5 MHz regardless of a network operator associated with a specific frequency band.
3GPP Long Term Evaluation (LTE), the latest wireless technology standard developed to support fourth generation (4G) communication systems, defines variable channel bandwidths selectable from 1.4 MHz to 20 MHz with constant subcarrier spacing of 15 kHz. Worldwide Interoperability for Microwave Access (WiMAX), another latest 4G wireless technology defined by 802.16m standards, supports channel bandwidths of 5, 7, 8.75, 10 and 20 MHz. Variable channel bandwidths allow for higher data rates and provide more flexibility to network operators. However, they add extra complexity to cell searches, resulting in longer service acquisition times and increased current drain of user device batteries.